Muffle etch injector assembly

ABSTRACT

A novel modular muffle etch injector assembly for use in a gas blanketed down-flow chemical vapor deposition apparatus of the type having a muffle and a modular gas injector assembly for introducing chemical vapors into a deposition chamber, the muffle being adapted for receiving and supporting the gas injector assembly, wherein deposition material residue collects on a lower surface of the muffle. The etch injector assembly of the present invention comprises an etch chamber having vertical sidewalls, a closed top end and an open bottom end, a supply mechanism for introducing a liquid etchant into the etch chamber, and a sealing device disposed along the open end of the etch chamber for providing a seal between the etch chamber and the lower surface of the muffle to confine the etchant to the etch chamber. The etch injector assembly preferably also includes an exhaust means for removing chemical vapors from the etch chamber. The etch injector assembly is adapted to replace the gas injector assembly within the deposition chamber during maintenance operations for removing the residue from the lower surface of the muffle by introducing the liquid etchant into the etch chamber and on to the lower surface of the muffle.

FIELD OF THE INVENTION

The invention relates to an apparatus for removing deposition materialresidue that collects on the lower surface of the muffle in a gasblanketed down-flow type chemical vapor deposition reactor used in thefabrication of semiconductor devices.

BACKGROUND OF THE INVENTION

Semiconductor devices typically include patterned layers of electricallyconductive, non-conductive and semi-conductive materials stacked over asilicon wafer. The various layers of material are successively depositedon the wafer and etched into predefined patterns to form individualcomponent structures within the particular device being fabricated.Chemical vapor deposition ("CVD") reactors are commonly used fordepositing layers of material by introducing select reactant gases intoa controlled environment surrounding the wafer. One type of CVD reactor,referred to herein as a gas blanketed down-flow reactor, introduces thereactant gases downward through vertical channels over a waferpositioned horizontally beneath the channels. One such CVD reactor arethe Watkins Johnson Company Models WJ-996, WJ 999R 3.3 and WJ 999R 3.5.In this type of CVD reactor, a conveyor belt moves the wafers through anelongated box like chamber called a "muffle." The conveyor belt travelsalong and is supported by the lower surface of the muffle. Multiplechemical vapor deposition chambers are located within the muffle. Amodular gas injector assembly is positioned at each deposition chamber.The gas injector assembly introduces reactant gases into the depositionchamber. The wafers on the conveyor belt travel through each depositionchamber wherein the surface of the wafer is exposed to the gases andcoated with the desired materials. Each gas injector assembly includesan array of plenums and passageways for properly mixing and directingthe gases to the surface of the wafers. The injector assemblies alsoinclude exhaust ports for removing chemical vapors from the depositionchamber.

During the deposition process, deposition material residue collects onthe conveyor belt and on the lower surface of the muffle within thedeposition chambers. The residue is continuously removed from theconveyor belt by passing the belt through an etching station outside themuffle. Excessive residue build-up on the lower surface of the mufflecan cause the conveyor belt to move unevenly through the depositionchambers, thereby adversely affecting the uniformity of the materialsdeposited on the surface of the wafers. Consequently, the reactor isperiodically shut down to remove the residue that has collected on thelower surface of the muffle. During this shutdown, the conveyor belt isremoved from the muffle and the gas injector assemblies are replacedwith etch injector assemblies. Presently, so far as applicant is aware,etch injector assemblies for gas blanketed down-flow type reactors suchas the Watkins Johnson models noted above are constructed to introduce avaporized etchant into the deposition chamber and on to the exposedlower surface of the muffle to etch away the deposition materialresidue. In order to reduce the time necessary to clean the muffle andthereby minimize the time the reactor is out of production, it isdesirable to use a liquid etchant to remove the residue from the muffle.The present invention is directed to the etch injector assembly thatallows for the introduction of a liquid etchant into an etch chamber andon to the lower surface of the muffle to more rapidly remove depositionmaterial residue from the muffle.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the invention to introduce a liquidetchant directly on to the lower surface of the muffle of a gasblanketed down-flow CVD reactor during maintenance operations to removedeposition material residue that has collected on the lower surface ofthe muffle.

It is another object to provide a sealed and self-contained etch chamberfor use with a liquid etchant.

It is a further object to provide a modular etch injector assemblyadapted to replace modular gas etch injector assemblies used in gasblanketed down-flow CVD reactors during such maintenance operations.

These and other objects are achieved by a novel modular muffle etchinjector assembly for use in a gas blanketed down-flow chemical vapordeposition apparatus of the type having a muffle and a modular gasinjector assembly for introducing chemical vapors into a depositionchamber, the muffle being adapted for receiving and supporting the gasinjector assembly, wherein deposition material residue collects on alower surface of the muffle. The etch injector assembly of the presentinvention comprises an etch chamber having vertical sidewalls, a closedtop end and an open bottom end, a supply mechanism for introducing aliquid etchant into the etch chamber, and a sealing device disposedalong the open end of the etch chamber for providing a seal between theetch chamber and the lower surface of the muffle to confine the etchantto the etch chamber. The etch injector assembly preferably also includesan exhaust means for removing chemical vapors from the etch chamber. Theetch injector assembly is adapted to replace the gas injector assemblywithin the deposition chamber during maintenance operations for removingthe residue from the lower surface of the muffle by introducing theliquid etchant into the etch chamber and on to the lower surface of themuffle.

In another aspect of the invention, the etch injector assembly comprisesa box-shaped etch chamber having a rectangular cross section and beingopen at its bottom end. The etch chamber is characterized by opposingsidewalls, opposing endwalls extending between the sidewalls, and a topcover plate attached to the sidewalls and endwalls. Inlet and exhaustports are formed in the cover plate. The liquid etchant is introducedinto the etch chamber through the inlet port. Chemical vapors areremoved from the etch chamber through the exhaust port. A sealing devicesuch as an "O" ring is positioned along the bottom surfaces of thesidewalls and endwalls for providing a seal between the open end of theetch chamber and the lower surface of the muffle to confine the etchantto the etch chamber. The etch injector assembly is sized and shaped toreplace the gas injector assembly during maintenance operations forremoving the residue from the lower surface of the muffle by introducingthe liquid etchant into the etch chamber and on to the lower surface ofthe muffle.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description that follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective schematic representation of a gas blanketeddown-flow chemical vapor deposition reactor.

FIG. 2 is a cross-section schematic representation of a gas blanketeddown-flow chemical vapor deposition reactor.

FIG. 3 is a cross-section schematic representation of a gas injectorassembly and deposition chamber for a gas blanketed down-flow chemicalvapor deposition reactor.

FIG. 4 is a perspective view of a muffle etch injector assemblyconstructed according to the preferred embodiment of the invention.

FIG. 5 is a cross-section view of the muffle etch injector assemblyinstalled in the muffle sleeve of a gas blanketed down-flow chemicalvapor deposition reactor.

The figures are not meant to be actual views of the various embodiments,but merely idealized representations used to depict the structure of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-3 illustrate the pertinent portions of a typical gas blanketeddown flow CVD reactor into which the muffle etch injector assembly ofthe present invention may be incorporated. Referring first to FIGS. 1and 2, a conveyor belt 10 carries semiconductor wafers 12 through adeposition chamber 14 in muffle 16. The CVD reactor will typicallyinclude several similarly constructed deposition chambers spacedsequentially along the muffle. Belt 10 is supported by the lower surface18 of muffle 16 and conveyed by rollers 20. Heating elements 22 arepositioned under the lower surface 18 of muffle 16 to heat the interiorof muffle 16.

Referring to FIG. 3, the upright walls 24 of the muffle 16 form arectangular box-like sleeve 26 to receive and support a modular gasinjector assembly 28. The gas injector assembly 28 introduces reactantgases into deposition chamber 14 through a series of plenums andpassageways as indicated by gas arrows 30 in FIGS. 1-3. An inert purgegas, typically nitrogen, is introduced into the deposition chamber 14along curtains 32 immediately before and after the gas injector assembly28, as indicated by purge arrows 34. Chemical vapors are removed fromthe deposition chamber 14 through exhaust tube 36 as indicated byexhaust arrows 38.

During operation, deposition materials collect on the conveyor belt 10carrying the wafers 12 and on the supporting lower surface 18 of themuffle 16 that is exposed to the reactant gases within depositionchamber 14. These residual deposition materials are continuously removedfrom the conveyor belt 10 by passing the belt through an etching station(not shown) outside the reactor. The residue that collects on the lowersurface 18 of the muffle 16 is periodically removed by shutting down thereactor, removing the gas injector assembly 28, and replacing it with amuffle etch injector assembly that introduces an etchant into thedeposition chamber 14 and on to the lower surface 18 of the muffle 16.So far as applicant is aware, muffle etch injector assemblies haveheretofore introduced a vaporized etchant into the deposition chamber inmuch the same way the deposition gases are used. Although othermaintenance operations may be performed on the reactor during the timethe reactor is shut down and out of production, the muffle etch isusually the most time consuming maintenance operation.

The muffle etch injector assembly of the present invention, illustratedin FIGS. 4 and 5, provides for the introduction of a liquid etchantdirectly on to the lower surface 18 of the muffle 16 in a self containedand sealed environment, thereby reducing the time required to remove theresidue from the muffle and minimizing the time the reactor is out ofproduction. Referring to FIGS. 4 and 5, modular muffle etch injectorassembly 40 includes a box shaped etch chamber 42 and a top cover plate44. Etch chamber 42 is defined by opposing sidewalls 46 and opposingendwalls 48 that extend between sidewalls 46. Cover plate 44 is attachedto and extends beyond the top surfaces 50 of sidewalls 46 and endwalls48. Etch chamber 42 is sized and shaped to fit within sleeve 26 ofmuffle 16 and to extend down to the lower surface 18 of the muffle 16when the etch injector assembly 40 is installed in the reactor. Thatportion of cover plate 44 extending beyond sidewalls 46 and endwalls 48forms a flange area 52 that rests on flange support 54 of sleeve 26. Inthis way, muffle etch assembly 40 can be installed in place of the gasinjector assembly 28 during maintenance operations on the reactor.

An "O" ring 56 or other suitable sealing device is positioned in recess58 along the bottom surfaces 60 of sidewalls 46 and endwalls 48 toprovide a seal between the open end of the etch chamber 40 and the lowersurface 18 of the muffle 16 to confine the etchant to the etch chamber.Cover plate 44 includes an inlet port 62, through which the liquidetchant is introduced into the etch chamber 42, and an exhaust port 64,through which chemical vapors are removed from the etch chamber 42.Preferably, cover plate 44 also includes a sight glass 66 through whichthe lower surface 18 of the muffle 16 may be observed. One of thedisadvantages of the prior art etch injector assemblies is the inabilityto readily monitor the removal of residue from the muffle. Previously,it was necessary to remove the etch injector assembly to determinewhether the removal was complete. Sight glass 66 allows the operator toreadily determine the progress of the etch without removing the etchinjector assembly.

The liquid etchant is preferably supplied by means of a local reservoir68, a conduit 70 connected to the reservoir 68 and the inlet port 62,and a valve 72 in conduit 70. Reservoir 68, conduit 70 and valve 72 arereferred to herein jointly as the etchant supply assembly. An optionaladapter 80 couples the conduit 70 to the inlet port 62. Valve 72 isoperative to move from an open position in which the etchant flows fromthe reservoir 68 through the conduit 70 into the etch chamber 42, to aclosed position in which the etchant is prevented from flowing from thereservoir 68. Exhaust tube 74 is attached to exhaust port 64 tofacilitate the removal of chemical vapors generated during etching ofthe muffle 16. Preferably, exhaust tube 74 is sized, shaped andpositioned for easy connection to the exhaust system already in place toremove chemical vapors generated during material deposition.

The various components of the muffle etch injector assembly arepreferably made of Poly Vinylidene Flouride (PVDF) or any suitablestructural material that is resistant to the liquid etchant. Inoperation, and after the reactor is shutdown, the gas injector assemblyis removed from the reactor and replaced with the muffle etch injectorassembly. The etch injector assembly 40 is fixed in position by means ofnuts 76 and bolts 78 or other suitable fasteners. The exhaust tube 74 isattached to the reactor exhaust system (not shown) and the etchantsupply assembly is installed into the inlet port 62. The valve 72 isopened to allow the liquid etchant to flow into the etch chamber 42 andon to the lower surface 18 of the muffle 16. After the depositionmaterial residue has been removed from the muffle, the etch injectorassembly is removed from the reactor and the gas injector assemblyre-installed.

There has been shown and described a novel muffle etch injector assemblywhich provides for the introduction of a liquid etchant directly on tothe lower surface of the muffle in a self contained and sealedenvironment, thereby reducing the time required to remove the residuefrom the muffle. The particular embodiments shown in the drawings anddescribed herein are for purposes of example and should not be construedto limit the invention as set forth in the appended claims.

We claim:
 1. A modular muffle etch injector assembly for use in a gasblanketed down-flow chemical vapor deposition apparatus of the typehaving a muffle and a modular gas injector assembly for introducingchemical vapors into a deposition chamber, the muffle being adapted forreceiving and supporting the gas injector assembly, wherein depositionmaterial residue collects on a lower surface of the muffle, the etchinjector assembly comprising:a. an etch chamber having verticalsidewalls, a closed top end and an open bottom end; b. a supply meansfor introducing a liquid etchant into the etch chamber; and c. a sealingmeans disposed along the bottom end of the etch chamber for providing aseal between the etch chamber and the lower surface of the muffle toconfine the etchant to the etch chamber.
 2. An etch injector assemblyaccording to claim 1, further comprising an exhaust means for removingchemical vapors from the etch chamber.
 3. An etch injector assemblyaccording to claim 1, wherein the etch chamber is adapted to replace thegas injector assembly in the muffle during maintenance operations forremoving the residue from the lower surface of the muffle by introducingthe liquid etchant into the etch chamber and on to the lower surface ofthe muffle.
 4. An etch injector assembly according to claim 1, furthercomprising a viewing means in the etch chamber for viewing the lowersurface of the muffle.
 5. A modular muffle etch injector assembly foruse in a gas blanketed down-flow chemical vapor deposition apparatus ofthe type having a muffle and a modular gas injector assembly forintroducing chemical vapors into a deposition chamber, the muffle beingadapted for receiving and supporting the gas injector assembly, whereindeposition material residue collects on a lower surface of the muffle,the etch injector assembly comprising:a. a box-shaped etch chamberhaving a rectangular cross section and being open at a bottom end, theetch chamber comprising opposing sidewalls, opposing endwalls extendingbetween the sidewalls, and a top cover plate attached to the sidewallsand endwalls; b. an inlet port in the cover plate through which a liquidetchant may be introduced into the etch chamber; c. an exhaust port inthe cover plate through which chemical vapors may be removed from theetch chamber; and d. a sealing means disposed along bottom surfaces ofthe sidewalls and endwalls for providing a seal between the open end ofthe etch chamber and the lower surface of the muffle to confine theetchant to the etch chamber.
 6. A muffle etch injector assemblyaccording to claim 5, wherein the etch chamber is sized and shaped toreplace the gas injector assembly in the muffle during maintenanceoperations for removing the residue from the lower surface of the muffleby introducing the liquid etchant into the etch chamber and on to thelower surface of the muffle.
 7. A muffle etch injector assemblyaccording to claim 5, further comprising a supply means for introducingthe liquid etchant into the etch chamber through the inlet port.
 8. Amuffle etch injector assembly according to claim 5, wherein the sealingmeans comprises an "O" ring disposed in a recess along the bottomsurfaces of the sidewalls and the endwalls.
 9. A muffle etch injectorassembly according to claim 5, further comprising an exhaust meansconnected to the exhaust port for removing chemical vapors from the etchchamber.
 10. An etch injector assembly according to claim 5, furthercomprising a viewing means in the etch chamber for viewing the lowersurface of the muffle.
 11. A muffle etch injector assembly according toclaim 5, wherein the sidewalls, endwalls and cover plate are made ofpoly vinylidene flouride (PVDF) material.
 12. A muffle etch injectorassembly according to claim 6, wherein the cover plate includes a flangearea extending laterally beyond the sidewalls and endwalls, the flangearea being adapted to support the etch injector assembly when it isinstalled in the muffle.
 13. A muffle etch injector assembly accordingto claim 7, wherein the supply means comprises a reservoir for storingliquid etchant, a conduit connected to the reservoir and a valvedisposed within the conduit, the valve being operative to move from anopen position in which the etchant flows from the reservoir through theconduit into the etch chamber to a closed position in which the etchantis prevented from flowing from the reservoir.
 14. A muffle etch injectorassembly according to claim 10, wherein the viewing means comprises asight glass disposed on the cover plate.